The foot drop could be from the lumbar back L4,L5,S1. What diagnostic tests have you Had?

The foot drop can also come from knots in muscles, (myofascial trigger points) in the lower leg and above the hip.

Muscles can restrict blood flow and entrap nerves, therefore function.

Specific muscles for foot drop are the tibialis anterior
http://triggerpoints.net/userfiles/Tibialis_Ant.jpg

and tibialis posterior
http://triggerpoints.net/userfiles/Tibialis_Pos.jpg

along with other muscles.

the Peronial nerve which impacts the area you describe can be restricted by the Peroneus Longus and Extensor Digitorum longus muscles which cause remote trigger points in the Peroneus brevis, Peroneus Teritus, Extensor digitorum longus, Extensor Hallis Brevis and Extensor Digitorum Brevis.

Therefore, these muscles need treated via direct pressure in the shortened position and then stretched via sitting in a chair or standing by placing the foot in plantar flection (toes tucked under) and roll heel outward and then inward, you can push the bottom of the heel with you hand in a seated position..

Look at these trigger points at:
http://triggerpoints.net/_sgg/m2m3_1.htm


Hope this helps.